The Iron K Line Profile of IRAS 18325-5926

IRAS 18325-5926 is an X-ray bright, Compton-thin, type-2 Seyfert galaxy and it was the first Seyfert 2 in which the presence of a broad Fe K-alpha emission line was claimed. However, although the structure of the Fe line appears broad, there is tentative evidence that it may comprise multiple lines. Nevertheless, previous analyses have only consisted of fitting standalone broad components to the Fe K band. Here, we have analyzed all available X-ray CCD data from Suzaku, XMM-Newton and ASCA to fully investigate the nature of the emission complex by testing broad-band physical models and alternative hypotheses. We find that both a model consisting of broad, blurred reflection from an ionized accretion disc and a model consisting of cold, neutral reflection plus narrow emission lines from highly-ionized photoionized gas (log \xi = 3.5) offer statistically comparable fits to the data although the true reality of the Fe line cannot currently be determined with existing data. However, it is hoped that better quality data and improved photon statistics in the Fe K band will allow a more robust distinction between models to be made.Comment: Accepted by MNRAS; 13 pages; 10 figures; 2 table

Evidence for changes in the radiative efficiency of transient black hole X-ray binaries

We have used pointed RXTE data to examine the long-term X-ray light curves of six transient black hole X-ray binaries during their decay from outburst to quiescence. In most cases there is a period of exponential decay as the source approaches the soft-to-hard state transition, and another period of exponential decay following this transition as the source decays in the hard state. The e-folding times change around the time of the state transition, from typically approx 12 days at the end of the soft state to approx 7 days at the beginning of the hard state. This factor ~2 change in the decay timescale is expected if there is a change from radiatively efficient emission in the soft state to radiatively inefficient emission in the hard state, overlying an exponential decay in the mass accretion rate. This adds support to the idea that the X-ray emitting region is governed by radiatively inefficient accretion (such as an advection-dominated or jet-dominated accretion flow) during the fading hard state.Comment: 9 pages, 18 figures, accepted for publication in MNRAS, minor changes following proo

Tissue and organelle targeted transgene expression in plants

This research develops systems for tissue and organelle targeted transgene expression in commercial strawberry. Two approaches were taken to achieve this. I) the development of a root-specific expression system for nuclear transgenes and II) the development of plastid transformation methodologies for strawberry. FavRB7, a root-specific, RB7 tonoplast intrinsic protein homologue was isolated from strawberry root tissue using reverse transcnptase-polymerase chain reaction (RT-PCR). A 2.8 kb region of promoter sequence associated with the FavRB7 gene was isolated and cloned upstream of the β-glucuronidase (gusA) reporter gene. Transgenic strawberry and tobacco were produced harbouring the gusA gene under control of the FavRB7 gene promoter. Promoter activity in these lines was characterised using histochemical, fluorometric and RNA molecular assays. FavRB7 promoter activity was shown to be strong and near root-specific in strawberry. However in contrast, in the heterologous species tobacco, FavRB7 promoter activity was shown to be constitutive. A series of novel plastid transformation vectors, harbouring selectable and scorable marker genes under control of strawberry plastome regulatory elements, were created to enable plastid transformation in strawberry and tobacco. Plastid transformation methodologies were developed for strawberry utilising the aminoglycoside 3'-adenyltransferase (aadA) gene and spectinomycin selection. Additionally, plastid transformation using a non-antibiotic selection system was investigated utilising the xylose isomerase (xylA) gene and D-xylose selection. Heteroplasmic plastid transformed strawberry lines were recovered using both selection systems and expression of the soluble modified green fluorescent protein (smGFP) scorable marker gene visualised specifically in strawberry chloroplasts of three individual lines. Additionally, heteroplasmic plastid transformed tobacco lines harbouring transgenes under control of strawberry plastome regulatory elements were generated using spectinomycin selection

Imprints of a high velocity wind on the soft x-ray spectrum of PG 1211+143

An extended XMM-Newton observation of the luminous narrow line Seyfert galaxy PG 1211+143 in 2014 has revealed a more complex high velocity wind, with components distinguished in velocity, ionization level, and column density. Here we report soft x-ray emission and absorption features from the ionized outflow, finding counterparts of both high velocity components, v ~ 0.129c and v ~ 0.066c, recently identified in the highly ionized Fe K absorption spectrum. The lower ionization of the co-moving soft x-ray absorbers imply a distribution of higher density clouds embedded in the main outflow, while much higher column densities for the same flow component in the hard x-ray spectra suggest differing sight lines to the continuum x-ray source.Comment: 8 pages, 5 figures, 4 tables; Accepted for publication in MNRA

Discovery of a ~5 day characteristic timescale in the Kepler power spectrum of Zw 229-15

We present time series analyses of the full Kepler dataset of Zw 229-15. This Kepler light curve --- with a baseline greater than three years, composed of virtually continuous, evenly sampled 30-minute measurements --- is unprecedented in its quality and precision. We utilize two methods of power spectral analysis to investigate the optical variability and search for evidence of a bend frequency associated with a characteristic optical variability timescale. Each method yields similar results. The first interpolates across data gaps to use the standard Fourier periodogram. The second, using the CARMA-based time-domain modeling technique of Kelly et al. (2014), does not need evenly-sampled data. Both methods find excess power at high frequencies that may be due to Kepler instrumental effects. More importantly both also show strong bends ({\Delta}{\alpha} ~ 2) at timescales of ~5 days, a feature similar to those seen in the X-ray PSDs of AGN but never before in the optical. This observed ~5 day timescale may be associated with one of several physical processes potentially responsible for the variability. A plausible association could be made with light-crossing, dynamical or thermal timescales, depending on the assumed value of the accretion disk size and on unobserved disk parameters such as {\alpha} and H/R. This timescale is not consistent with the viscous timescale, which would be years in a ~10^7 Solar mass AGN such as Zw 229-15. However there must be a second bend on long (>~1 year) timescales, and that feature could be associated with the viscous timescale.Comment: 10 pages, 5 figures, 1 table. To appear in the Astrophysical Journal, Part

A Phase Coded Disk Approach To Thick Curvilinear Line Detection

This paper examines the well-known problem of line detection, but where the lines are wider than one pixel. The motivation behind the paper is the extraction of road information from high resolution photogrammetry and Light Detection and Ranging (LIDAR) data. Wide lines cause varying problems during detection. The Hough or Radon transform approaches do not find the road centrelines accurately; diagonals of the thick lines are found instead whilst other methods also tend to be error prone. Our approach convolves a raw, pixelated, binary road classification with a complex-valued disk. The technique provides three separate pieces of information about the road or thick line: the centreline, the direction and the width of the road at any point along the centreline. The road centreline can be detected from the position of the peak of the magnitude image resulting from the complex convolution. Road width can also be estimated from the magnitude peak whilst the direction of the road may be obtained from the phase image